What Does P1251 Mean?
DTC P1251 indicates the cold-start injector circuit is shorted to the positive voltage supply (B+). The wiring or injector solenoid that provides additional fuel during cold engine starts has developed a short to the battery voltage line. This can cause the cold-start injector to remain energized continuously or operate when not commanded, potentially flooding the engine with excess fuel during starts.
Common Causes
30%
Cold-start injector wiring shorted to a B+ wire in the harness
25%
Cold-start injector solenoid with internal short to the power terminal
20%
Connector damage allowing cross-pin contact between signal and power pins
15%
Aftermarket wiring modification creating unintended short to B+
10%
Heat-damaged insulation on wiring near the engine allowing B+ contact
Diagnostic Steps
1
Disconnect the cold-start injector connector and measure voltage on the PCM control wire — if battery voltage is present with the injector disconnected, the wire is shorted to B+ somewhere in the harness.
2
Inspect the cold-start injector wiring for insulation damage, particularly where it routes near hot exhaust components or positive battery cables.
3
Measure the cold-start injector solenoid resistance and check for shorts between the coil terminals and the injector housing/body.
4
Trace the wiring harness from the cold-start injector back to the PCM, checking for areas where the control wire may be pinched against or touching a power supply wire.
5
Check the injector connector for melted plastic or pin-to-pin shorts caused by heat exposure.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
DTC P1251 indicates the cold-start injector circuit is shorted to the positive voltage supply (B+). The wiring or injector solenoid that provides additional fuel during cold engine starts has developed a short to the battery voltage line. This can cause the cold-start injector to remain energized co...
The most common cause of P1251 (Start Of Cold Start Injector Short To Positive) is: Cold-start injector wiring shorted to a B+ wire in the harness
Typical repair costs for P1251 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A cold-start injector shorted to B+ may continuously inject fuel, causing flooding, hard starting, and excessive fuel in the intake manifold. In extreme cases, raw fuel in the intake creates a fire risk, particularly if it contacts hot engine surfaces.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1251 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection / Cold Start
Difficulty
Type
Manufacturer
Recommended Tools
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